Mobile radio communication system, communication apparatus applied in a mobile radio communication system, and mobile radio communication method

ABSTRACT

In the mobile radio communication system where the UMTS and an another system coexist an idle slot for observing the frequency component of another system is inserted in one superframe of UMTS. The duration of this idle slot is at most half of the duration of one frame that form the superframe and it is inserted at an interval of a specified number of frames. Therefore, the frequency component of the another system can be observed securely from the UMTS. Further, the deterioration of interleaving performance of the compressed mode frames during such observation can be suppressed.

This application is a continuation of International ApplicationPCT/JP99/01051, with an international filing date of Mar. 4, 1999, whichdesignated the United States, the entire contents of which are herebyincorporated by references.

TECHNICAL FIELD

The present invention relates to a mobile radio communication system inwhich UMTS (Universal Mobile Terrestrial communication System) and GSM(Group Specific Mobile) system coexist, communication apparatus appliedin mobile radio communication system, and mobile radio communicationmethod. More particularly this invention, relates to a technology ofobserving the control channel of a GSM system that is another system inthe mobile radio communication system by making use of an idle period.

BACKGROUND ART

In a CDMA cellular system, because the same carrier frequency is usedrepeatedly in every cell there is no need for handovers betweenfrequencies within the same system. However, considering a case such aswhen existing systems are present together, there is a need forhandovers between different carrier frequencies. Three points pertainingto detailed cases are described below.

As a first point, in a cell where there is considerable traffic, aseparate carrier frequency is used to accommodate the increased numberof subscribers, and a handover may be performed between those cells. Asa second point, when an umbrella cell constitution is used, differentfrequencies are allocated to large and small cells, and handovers areperformed between the cells. Then, as a third point, there are cases ofhandovers between a third generation system, such as a W (Wideband)-CDMAsystem, and a second-generation system, such as a current mobiletelephone system.

When performing handovers in cases such as those mentioned above, it isnecessary to detect the power of carriers at the different frequencies.To achieve this detection, the receiver need only have a structurecapable of detecting two frequencies. However, this increases the sizeof the constitution of the receiver, or makes the constitutioncomplicated.

Furthermore, two types of handover method may be considered: a mobileassisted handover (MAHO) and a network assisted handover (NAHO).Comparing the MAHO and NAHO methods, NAHO reduces the burden of themobile device. However, it is necessary to synchronize the mobile deviceand the base station, whereby the constitution of the base station andthe network becomes complicated and large in order to be capable oftracking each dedicated mobile device.

For such reasons, the realization of the MAHO method is more desirable,but to determine whether or not to handover, it is necessary to measurethe strength of carriers of different frequencies at the mobile devices.However, a CDMA cellular system differs from a time division multipleaccess (TDMA) system used in a second generation, in that it usesordinarily continuous transmission for both transmission/reception. Inthis continuous transmission/reception technique, unless receiverscorresponding to two frequencies are prepared, it is necessary to stopthe timing of the transmission or the reception and measure the otherfrequency.

There has been disclosed a technique relating to a compressed modemethod, for time-compressing the transmission data in the normal modeand transmitting it in a short time, thereby creating some spare timewhich can be utilized to measure the other frequency carrier. As anexample of this, there is Japan Patent Application National Publication(Laid-Open) (JP-A) No. 8-500475 “Non-continuous Transmission forSeamless Handovers in DS-Mobile Radio Communications Systems”. Thisapplication discloses a method of realizing a compressed mode, whereinthe spreading factor of the spreading code used is lowered to compressthe transmission timing.

The method of realizing the compressed mode according to the aboveapplication will be explained below. FIG. 13 shows an example oftransmissions in a normal mode and a compressed mode in a conventionalCDMA system. In FIG. 13, the vertical axis represents transmissionrate/transmission power, and the horizontal axis represents time. In theexample of FIG. 13, the compressed mode transmission is inserted betweennormal transmission frames. In the transmission in the compressed mode,a non-transmission period is provided in the downlink frame, and can beset to a desired period of time (duration). This non-transmission periodrepresents idle period during which the strength of the other frequencycarrier is measured. In this way, slot transmission can be achieved byinserting the idle period between transmission of compressed modeframes.

In this type of compressed mode transmission, transmission power isincreased in accordance with the time ratio between the idle period andthe frame (compressed mode frame) transmission duration. Therefore, asshown in FIG. 13, the compressed mode frame is transmitted at a highertransmission power than the frame in normal transmission. Consequently,transmission quality can be maintained even in frame transmission incompressed mode.

Usually, between the GSM and GSM, different frequency component (controlchannel) is observed by using one observation period (no-transmissionperiod) assigned in every one superframe. However, when a mobile radiocommunication system in which the UMTS and GSM systems coexist isconsidered, it requires operation for observing the frequency componentsbetween different systems, that is, from UMTS to GSM system. In thiscase, too, same as in the case of observation between GSM and GSM, anidle period for observing the frequency component of GSM is set in thesuperframe of the UMTS.

That is, for one frame of superframe in the UMTS, it is necessary toassign the observation period composed of the same number of idle slotsas in the case of GSM-GSM observation. However, in the existingtechnology, due to restrictions in the error correction code andspreading factor for frame transmission, it is difficult to insert allobservation period in one frame, and there are many other problems.Therefore, a technology for observing the frequency component of GSMsystem from the UMTS is expected in the future.

It is an object of the present invention to solve the problems mentionedabove by providing a mobile radio communication system, communicationapparatus applied in mobile radio communication system, and mobile radiocommunication method, capable of observing securely the frequencycomponent of an another system from the UMTS even when the UMTS and theanother system coexist, and suppressing deterioration of interleavingperformance of compressed mode frame in such a case.

SUMMARY OF THE INVENTION

The mobile radio communication system according to one aspect of theinvention is a mobile radio communication system comprising a firstcommunication system employing a code division multiple access method oftransmitting frames by using a first superframe which is formed of aplural frames which expresses a frame transmission period, and a secondcommunication system for observing frequency component of control datatransmission channel by making use of a specified idle period, thespecified idle period being inserted in a second superframe for downlinkuser data transmission channel on the basis of the difference betweenthe number of frames of integer multiple of second superframe expressinga frame transmission period in user data transmission channel and thenumber of frames of third superframe expressing a frame transmissionperiod in control data transmission channel, error correction andinterleaving of frames being performed when the first communicationsystem transmits the frames, wherein the specified idle period is atmost half of the time of one frame that forms the first superframe andinserted in the first superframe at intervals of a specified number offrames, and wherein the frequency component of control data transmissionchannel of the second communication system is observed from the firstcommunication system by making use of the idle period.

According to the above invention, when the first communication systemand second communication system coexist, since the idle period forobserving the frequency component of the second communication system isinserted at most in ½ time of one frame duration for composing onesuperframe of first communication system, at intervals of a specifiednumber of frames, it is not required to observe the frequency componentby one observation in one superframe, and the restrictions in frametransmission such as error correction code and spreading factor can besatisfied. Therefore, even when the first communication system andsecond communication system coexist, the frequency component of thesecond communication system can be securely observed from the firstcommunication system. Further, deterioration of interleaving performanceof the compressed mode frame during such observation can be suppressed.

In the mobile radio communication system according to another aspect ofthe invention, wherein the first communication system is the UMTS thattransmits frames by using a first superframe which is formed of a pluralframes and which expresses a frame transmission period, and wherein thesecond communication system is an another system that transmits framesby using a second superframe of an equal transmission period as thefirst superframe of the UMTS.

According to the above invention, in a case where the UMTS and anothersystem coexist, since the idle period for observing the frequencycomponent of the another system is inserted at most in ½ time of oneframe duration for composing one superframe of UMTS, at intervals of aspecified number of frames, it is not required to observe the frequencycomponent by one observation in one superframe, and the restrictions inframe transmission such as error correction code and spreading factorcan be satisfied. Therefore, even when the UMTS and another systemcoexist, the frequency component of the another system can be securelyobserved from the UMTS, and deterioration of interleaving performance ofthe compressed mode frame can be suppressed at this time. Besides, inthe invention, the first superframe corresponds to the one UMTSsuperframe mentioned in an embodiment described later, the secondsuperframe to the one GSM superframe, the third superframe to the oneFCCH/SCH superframe, the user data transmission channel to the dedicatedtraffic channel, and the control data transmission channel to the commoncontrol channel, respectively.

In the mobile radio communication system according to another aspect ofthe invention, the interval of a specified number of frames isdetermined according to the difference in the transmission periodbetween the UMTS and the another system.

According to the above invention, since the interval of a specifiednumber of frames is determined by the difference in the transmissionperiod between the UMTS and another system, the different frequencycomponents can be observed completely depending on the difference in thetransmission period.

In the mobile radio communication system according to another aspect ofthe invention, the specified idle period is placed in the center of theframe that is the unit of a superframe of the UMTS.

According to the above invention, since the idle period is placed in thecenter of the frame which is the unit of superframe of the UMTS, theinterleaving effect can be obtained securely.

The mobile radio communication system according to another aspect of theinvention is a mobile radio communication system comprising a firstcommunication system employing a code division multiple access method oftransmitting frames by using a first superframe which is formed of aplural frames and which expresses a frame transmission period, and asecond communication system for observing frequency component of controldata transmission channel by making use of a specified idle period, thespecified idle period being inserted in a second superframe for downlinkuser data transmission channel on the basis of the difference betweenthe number of frames of integer multiple of second superframe expressinga frame transmission period in user data transmission channel and thenumber of frames of third superframe expressing a frame transmissionperiod in control data transmission channel, error correction andinterleaving of frames is performed when the first communication systemtransmits the frames, wherein the specified idle period is at most halfof the time of one frame that forms the first superframe and inserted inthe first superframe at not necessarily regular intervals of a specifiednumber of slots, and wherein the frequency component of control datatransmission channel of the second communication system is observed fromthe first communication system by making use of the idle period.

According to the above invention, in the case where the firstcommunication system and second communication system coexist, since theidle period for observing the frequency component of the secondcommunication system is inserted at most in ½ time of one frame durationfor composing one superframe of first communication system, at intervalsof a specified number of slots, it is not required to observe thefrequency component by one observation in one superframe, and therestrictions in frame transmission such as error correction code andspreading factor can be satisfied. Therefore, even when the firstcommunication system and second communication system coexist, thefrequency component of the second communication system can be securelyobserved from the first communication system. Further, deterioration ofinterleaving performance of the compressed mode frame during suchobservation can be suppressed.

In the mobile radio communication system according to another aspect ofthe invention, wherein the first communication system is the UMTS thattransmits frames by using a first superframe which is formed of a pluralframes and which expresses a frame transmission period, and wherein thesecond communication system is an another system that transmits framesby using a second superframe of an equal transmission period as thefirst superframe of the UMTS.

According to the above invention, in the case where the UMTS and anothersystem coexist, since the idle period for observing the frequencycomponent of the another system is inserted at most in ½ time of oneframe duration for composing one superframe of UMTS, at intervals of aspecified number of slots, it is not required to observe the frequencycomponent by one observation in one superframe, and the restrictions inframe transmission such as error correction code and spreading factorcan be satisfied. Therefore, even when the UMTS and another systemcoexist, the frequency component of the another system can be securelyobserved from the UMTS, and deterioration of interleaving performance ofthe compressed mode frame can be suppressed. Besides, according to theinvention, the first superframe corresponds to the one UMTS superframementioned in the embodiment described later, the second superframe tothe one GSM superframe, the third superframe to the one FCCH/SCHsuperframe, the user data transmission channel to the dedicated trafficchannel, and the control data transmission channel to the common controlchannel, respectively.

In the mobile radio communication system according to another aspect ofthe invention, the interval of a specified number of slots is determinedaccording to the difference in the transmission period between the UMTSand the another system.

According to the above invention, since the interval of a specifiednumber of slots is determined by the difference in the transmissionperiod between the UMTS and another system, the different frequencycomponents can be observed completely depending on the difference in thetransmission period.

In the mobile radio communication system according to another aspect ofthe invention, the plural numbers of the specified idle periods areplaced in the UMTS superframe and the idle period may be differently setin each frame.

According to the above invention, since the plural idle periods in thesuperframe of the UMTS are placed separately in each frame, thenecessary idle duration is held in one superframe.

In the mobile radio communication system according to another aspect ofthe invention, the total of the idle period is equal to the specifiedidle period provided for observing the frequency component of theanother systems.

According to the above invention, since the total of the plural idleperiods is equal to the specified idle period provided for observing thefrequency component of the other systems, the total idle periods isequal to the observation duration of different frequencies between othersystems can be held in one superframe.

In the mobile radio communication system according to another aspect ofthe invention, the frame in which the specified idle period is insertedis compressed and transmitted intermittently.

According to the above invention, since the frame in which the specifiedidle time is inserted is compressed and transmitted intermittently, aframe transmission of a high decodability is realized even when an idleperiod is inserted in one frame period.

In the mobile radio communication system according to another aspect ofthe invention, the compressed frame is generated by increasing thecoding rate.

According to the above invention, since the compressed frame isgenerated by increasing the coding rate, the compression ratio islowered, and the number of spreading codes of a shorter code length canbe suppressed.

In the mobile radio communication system according to another aspect ofthe invention, the compressed frame is generated at a spreading factorthat is the same as the spreading factor at which a frame that do notcontain the specified idle period is generated.

According to the above invention, since the compressed frame isgenerated at a same spreading factor as another frame in which thespecified idle period is not inserted, the interference and noiseresistant characteristic to the compressed frame is assured.

The communication apparatus applied in a mobile radio communicationsystem according to another aspect of the invention is a communicationapparatus applied in a mobile radio communication system comprising afirst communication system employing a code division multiple accessmethod of transmitting frames by using a first superframe which isformed of a plural frames and which expresses a frame transmissionperiod, and a second communication system for observing frequencycomponent of control data transmission channel by making use of aspecified idle period, the specified idle period being inserted in asecond superframe for downlink user data transmission channel on thebasis of the difference between the number of frames of integer multipleof second superframe expressing a frame, transmission period in userdata transmission channel and the number of frames of third superframeexpressing a frame transmission period in control data transmissionchannel, error correction and interleaving of frames being performedwhen the first communication system transmits the frames, frames beingtransmitted continuously in the case of normal mode, and compressedframes being transmitted intermittently in the case of compressed mode,wherein the communication apparatus comprises a control unit forinserting a specified idle period, during the compressed mode, in thefirst superframe, having a duration that is at most portion of one framethat forms the first superframe, and at intervals of a specified numberof frames, and wherein the frequency component of control datatransmission channel of the second communication system is observed fromthe first communication system by making use of the specified idleperiod inserted by the control unit.

According to the above invention, in the case where the firstcommunication system and second communication system coexist, since itis controlled so that the idle period for observing the frequencycomponent of the second communication system is inserted at most in ½time of one frame duration for composing superframe in the superframe ofthe first communication system, it is not required to observe thefrequency component by one observation in one, superframe, and therestrictions in frame transmission such as error correction code andspreading factor can be satisfied. Therefore, even when the firstcommunication system and second communication system coexist, thefrequency component of the second communication system can be securelyobserved from the first communication system. Further, deterioration ofinterleaving performance of the compressed mode frame during suchobservation can be suppressed.

In the communication apparatus applied in a mobile radio communicationsystem according to another aspect of the invention, wherein the firstcommunication system is the UMTS that transmits frames by using a firstsuperframe which is formed of a plural frames and which expresses aframe transmission period, and wherein the second communication systemis an another system that transmits frames by using a second superframeof an equal transmission period as the first superframe of the UMTS.

According to the above invention, in the case where the UMTS and anothersystem coexist, since the idle period for observing the frequencycomponent of the another system is inserted at most in ½ time of oneframe duration for composing one superframe of UMTS, at intervals of aspecified number of frames, it is not required to observe the frequencycomponent by one observation in one superframe, and the restrictions inframe transmission such as error correction code and spreading factorcan be satisfied. Therefore, even when the UMTS and another systemcoexist, the frequency component of the another system can be securelyobserved from the UMTS, and deterioration of interleaving performance ofthe compressed mode frame can be suppressed. Besides, in the invention,the first superframe corresponds to the one UMTS superframe mentioned inthe embodiment described later, the second superframe to the one GSMsuperframe, the third superframe to the one FCCH/SCH superframe, theuser data transmission channel to the dedicated traffic channel, and thecontrol data transmission channel to the common control channel,respectively.

In the communication apparatus applied in a mobile radio communicationsystem according to another aspect of the invention, the control unitdetermines the interval of a specified number of frames according to thedifference in the transmission period between the UMTS and the anothersystem.

According to the above invention, since the interval of a specifiednumber of frames is determined by the difference in the transmissionperiod between the UMTS and another system at the time of controlling,the different frequency components can be observed completely dependingon the difference in the transmission period.

In the communication apparatus applied in a mobile radio communicationsystem according to another aspect of the invention, the control unitplaces the specified idle period in the center of the frame that is theunit of superframe of the UMTS.

According to the above invention, since the specified idle period isplaced in the center of the frame which is the unit of superframe of theUMTS at the time of controlling, the interleaving effect may be obtainedsecurely.

The communication apparatus applied in a mobile radio communicationsystem in a different aspect of the invention is a communicationapparatus applied in a mobile radio communication system comprising afirst communication system employing a code division multiple accessmethod of transmitting frames by using a first superframe which isformed of a plural frames and which expresses a frame transmissionperiod, and a second communication system for observing frequencycomponent of control data transmission channel by making use of aspecified idle period, the specified idle period being inserted in asecond superframe for downlink user data transmission channel, on thebasis of the difference between the number of frames of integer multipleof second superframe expressing a frame, transmission period in userdata transmission channel and the number of frames of third superframeexpressing a frame transmission period in control data transmissionchannel, error correction and interleaving of frames being performedwhen the first communication system transmits the frames, frames beingtransmitted continuously in the case of normal mode, and compressedframes being transmitted intermittently in the case of compressed mode,wherein the communication apparatus comprises a control unit forinserting a specified idle period, during the compressed mode, in thefirst superframe, having a duration that is at most portion of one framethat forms the first superframe, and at not necessarily regularintervals of a specified number of slots, and wherein the frequencycomponent of control data transmission channel of the secondcommunication system is observed from the first communication system bymaking use of the specified idle period inserted by the control unit.

According to the above invention, in the case where the firstcommunication system and second communication system coexist, since itis controlled so that the idle period for observing the frequencycomponent of the second communication system is inserted at most in ½time of one frame duration for composing superframe in the superframe ofthe first communication system and at an interval of a specified numberof slots, it is not required to observe the frequency component by oneobservation in one superframe, and the restrictions in frametransmission such as error correction code and spreading factor can besatisfied. Therefore, even when the first communication system andsecond communication system coexist, the frequency component of thesecond communication system can be securely observed from the firstcommunication system. Further, deterioration of interleaving performanceof the compressed mode frame during such observation can be suppressed.

In the communication apparatus applied in a mobile radio communicationsystem according to another aspect of the invention, the firstcommunication system is the UMTS that transmits frames by using whereinthe first communication system is the UMTS that transmits frames byusing a first superframe which is formed of a plural frames and whichexpresses a frame transmission period, and wherein the secondcommunication system is an another system that transmits frames by usinga second superframe of an equal transmission period as the firstsuperframe of the UMTS.

According to the above invention, in the case where the UMTS and anothersystem coexist, since the idle period for observing the frequencycomponent of the another system is inserted at most in ½ time of oneframe duration for composing one superframe of UMTS, at intervals of aspecified number of slots, it is not required to observe the frequencycomponent by one observation in one superframe, and the restrictions inframe transmission such as error correction code and spreading factorcan be satisfied, and therefore even when the UMTS and another systemcoexist, the frequency component of the another system can be securelyobserved from the UMTS, and deterioration of interleaving performance ofthe compressed mode frame can be suppressed. Besides, according to theinvention, the first superframe corresponds to the one UMTS superframementioned in the embodiment described later, the second superframe tothe one GSM superframe, the third superframe to the one FCCH/SCHsuperframe, the user data transmission channel to the dedicated trafficchannel, and the control data transmission channel to the common controlchannel, respectively.

In the communication apparatus applied in a mobile radio communicationsystem according to another aspect of the invention, the control unitdetermines the interval of a specified number of frames according to thedifference in the transmission period between the UMTS a nd the anothersystem.

According to the above invention, since the interval of a specifiednumber of slots is determined by the difference in the transmissionperiod between the UMTS and another system at the time of controlling,different frequency components can be observed completely depending onthe difference in the transmission period.

In the communication apparatus applied in a mobile radio communicationsystem according to another aspect of the invention, the control unitprovides the specified idle period at many places in the UMTS superframeand the sets each idle period differently in each frame.

According to the above invention, since plural idle periods are disposedin each frame in the superframe of the UMTS at the time of controlling,a necessary idle duration can be held in one superframe.

In the communication apparatus applied in a mobile radio communicationsystem according to another aspect of the invention, the control unitsets the idle period in such a way that the total of then is equal tothe specified idle duration provided for observing the frequencycomponent between the another systems.

According to the above invention, since the total of the plural idleperiods is set equal to the specified idle duration provided forobserving the frequency component between the other systems at the timeof controlling, an idle duration equal to observation of differentfrequencies between other systems can be held in one superframe.

In the communication apparatus applied in a mobile radio communicationsystem according to another aspect of the invention, the control unitincreases the coding rate when generating the compressed frame.

According to the above invention, since the compressed frame isgenerated by increasing the coding rate at the time of controlling, thecompression ratio is lowered, and the number of spreading codes of ashorter code length can be suppressed.

In the communication apparatus applied in a mobile radio communicationsystem according to another aspect of the invention, the control unitsets a spreading factor when generating the compressed mode frame thatis the same as the spreading factor at which a frame that do not containthe specified idle period is generated.

According to the above invention, since the compressed frame isgenerated at a same spreading factor as another frame in which thespecified idle period is not inserted at the time of controlling, theinterference and noise resistant characteristic of the compressed frameis assured.

In the communication apparatus applied in a mobile radio communicationsystem according to another aspect of the invention, the control unitincreases the average transmission power during the compressed mode.

According to the above invention, since the average transmission poweris increased in the compressed mode at the time of controlling, thecharacteristic deterioration may be suppressed to a minimum limit.

The mobile radio communication method according to another aspect of theinvention is a mobile radio communication method, applied in a mobileradio communication system having, a first communication systememploying a code division multiple access method of transmitting framesby using a first superframe which is formed of a plural frames and whichexpresses a frame transmission period, and a second communication systemfor observing frequency component of control data transmission channelby making use of a specified idle period, the specified idle periodbeing inserted in a second superframe for downlink user datatransmission channel on the basis of the difference between the numberof frames of integer multiple of second superframe expressing a frametransmission period in user data transmission channel and the number offrames of third superframe expressing a frame transmission period incontrol data transmission channel, error correction and interleaving offrames being performed when the first communication system transmits theframes, frames being transmitted continuously in the case of normalmode, and compressed frames being transmitted intermittently in the caseof compressed mode, the method comprising a first step of compressingframes to be transmitted intermittently during the compressed mode, anda second step of transmitting the frames compressed in the first stepintermittently by inserting a specified idle period, in the firstsuperframe, having a duration that is at most portion of one frame thatforms the first superframe, and at intervals of a specified number offrames determined by the relation of the frame structure between thefirst communication system and the second communication system, and thefrequency component of control data transmission channel of the secondcommunication system being observed from the first communication systemby making use of the specified idle period inserted in the second step.

According to the above invention, by compressing the frames transmittedintermittently at the time of compressed mode, and inserting an idleperiod for observing the frequency component of the second communicationsystem at most in ½ time of one frame duration for composing thesuperframe of the first communication system in the superframe of thefirst communication system and at an interval of a specified number offrames determined by the relation of the frame structure between thefirst communication system and second communication system, since thestep for transmitting intermittently the compressed frames is set up, itis not required to observe the frequency component by one observation inone superframe, and the restrictions in frame transmission such as errorcorrection code and spreading factor can be satisfied. Therefore evenwhen the first communication system and second communication systemcoexist, the frequency component of the second communication system canbe securely observed from the first communication system. Further,deterioration of interleaving performance of the compressed mode frameduring such observation can be suppressed.

The mobile radio communication method according to another aspect of theinvention is a mobile radio communication method, applied in a mobileradio communication system having, a first communication systememploying a code division multiple access method of transmitting framesby using a first superframe which is formed of a plural frames and whichexpresses a frame transmission period, and a second communication systemfor observing frequency component of control data transmission channelby making use of a specified idle period, the specified idle periodbeing inserted in a second superframe for downlink user datatransmission channel on the basis of the difference between the numberof frames of integer multiple of second superframe expressing a frametransmission period in user data transmission channel and the number offrames of third superframe expressing a frame transmission period incontrol data transmission channel, error correction and interleaving offrames being performed when the first communication system transmits theframes, frames being transmitted continuously in the case of normalmode, and compressed frames being transmitted intermittently in the caseof compressed mode, the method comprising a first step of compressingframes to be transmitted intermittently during the compressed mode, anda second step of transmitting the frames compressed in the first stepintermittently by inserting a specified idle period, in the firstsuperframe, having a duration that is at most half of one frame thatforms the first superframe, and at intervals of a specified number ofslots determined by the relation of the frame structure between thefirst communication system and the second communication system, and thefrequency component of control data transmission channel of the secondcommunication system being observed from the first communication systemby making use of the specified idle period inserted in the second step.

According to the above invention, by compressing the frames transmittedintermittently at the time of compressed mode, and inserting an idleperiod for observing the frequency component of the second communicationsystem at most in ½ time of one frame duration for composing thesuperframe of the first communication system in the superframe of thefirst communication system and at an interval of a specified number ofslots determined by the relation of the frame structure between thefirst communication system and second communication system, since thestep for transmitting intermittently the compressed frames is set up, itis not required to observe the frequency component by one observation inone superframe, and the restrictions in frame transmission such as errorcorrection code and spreading factor can be satisfied. Therefore evenwhen the first communication system and second communication systemcoexist, the frequency component of the second communication system canbe securely observed from the first communication system. Further,deterioration of interleaving performance of the compressed mode frameduring such observation can be suppressed.

In the mobile radio communication method in another aspect of theinvention, the first communication system is the UMTS that transmitsframes by using a first superframe expressing a frame transmissionperiod, wherein the first communication system is the UMTS thattransmits frames by using a first superframe which is formed of a pluralframes and which expresses a frame transmission period, and wherein thesecond communication system is an another system that transmits framesby using a second superframe of an equal transmission period as thefirst superframe of the UMTS.

According to the above invention, in particular, in the case where theUMTS and another system coexist, since the idle period for observing thefrequency component of the another system is inserted at most in ½ timeof one frame duration for composing one superframe of UMTS, at intervalsof a specified number of frames or at an interval of a specified numberof slots, it is not required to observe the frequency component by oneobservation in one superframe, and the restrictions in frametransmission such as error correction code and spreading factor can besatisfied, and therefore even when the UMTS and another system coexist,the frequency component of the another system can be securely observedfrom the UMTS, and deterioration of interleaving performance of thecompressed mode frame can be suppressed. Besides, according to theinvention, the first superframe corresponds to the one UMTS superframementioned in the embodiment described later, the second superframe tothe one GSM superframe, the third superframe to the one FCCH/SCHsuperframe, the user data transmission channel to the dedicated trafficchannel, and the control data transmission channel to the common controlchannel, respectively.

In the mobile radio communication method according to another aspect ofthe invention, the compressed frames are generated in the first step byincreasing the coding rate.

According to the above invention, since the compressed frame isgenerated by increasing the coding rate at this step, the compressionratio is lowered, and the number of spreading codes of a shorter codelength can be suppressed.

In the mobile radio communication method according to another aspect ofthe invention, the compressed frame is generated in the first step at aspreading factor that is the same as the spreading factor at which aframe that do not contain the specified idle period is generated.

According to the above invention, since the compressed frame isgenerated at a same spreading factor as another frame in which thespecified idle period is not inserted at this step, the interference andnoise resistant characteristic to the compressed frame is assured.

In the mobile radio communication method according to another aspect ofthe invention, average transmission power is increased in the secondstep during the compressed mode.

According to the above invention, since the average transmission poweris increased in the compressed mode at this step, the characteristicdeterioration may be suppressed to a minimum limit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a frame format applied in a GSM system, FIG. 1(a) is adiagram for explaining the frame format of dedicated traffic channel,and FIG. 1(b) is a diagram for explaining the frame format of commoncontrol channel;

FIG. 2 is a diagram for explaining the observation period of GSMsuperframe applied in the GSM system;

FIG. 3 shows an observation method of different frequency componentsbetween GSM and GSM, FIG. 3(a) is a diagram for explaining the frameformat of common control channel, FIG. 3(b) is a diagram for explainingthe frame format of dedicated traffic channel in relation to the commoncontrol channel, and FIG. 3(c) is a diagram for explaining theobservation period inserted in every GSM superframe;

FIG. 4 is a diagram for explaining an observation method in the GSMsystem;

FIG. 5 show a frame format applied in the UMTS, FIG. 5(a) is a diagramfor explaining the frame format of dedicated traffic channel applied inthe GSM system, and FIG. 5(b) is a diagram for explaining the format ofsuperframe of UMTS;

FIG. 6 shows an observation method of different frequency componentsbetween GSM and UMTS, FIG. 6(a) is a diagram for explaining the frameformat of common control channel applied in the GSM system, FIG. 6(b) isa diagram for explaining the relation of superframe between the UMTS andGSM systems, and FIG. 6(c) is a diagram for explaining the observationperiod inserted in every superframe in the UMTS;

FIG. 7 is a diagram for explaining the frame transmission of downlinkaccording to a first embodiment of the invention;

FIG. 8 is a block diagram showing a mobile radio communication systemaccording to the first embodiment of the invention;

FIG. 9 is a flowchart for explaining the transmission operation incompressed mode according to the first embodiment of the invention;

FIG. 10 is a flowchart for explaining the reception operation incompressed mode according to the first embodiment of the invention;

FIG. 11 is a diagram for explaining the frame transmission of downlinkaccording to a second embodiment of the invention;

FIG. 12 is a diagram for explaining the frame transmission of downlinkaccording to a third embodiment of the invention; and

FIG. 13 is a diagram for explaining the frame transmission of downlinkin a prior art.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring now to the accompanying drawings, preferred embodiments ofmobile radio communication system, communication apparatus applied inmobile radio communication system, and mobile radio communication methodof the invention are described in detail below.

First, the principle of a first embodiment of the invention isdescribed. In the first embodiment of the invention, a mobile radiocommunication system in which UMTS and GSM systems coexist is presentedas an example. To begin with, the existing system, GSM system, isexplained. FIG. 1 shows a frame format applied in the GSM system. Morespecifically, FIG. 1(a) is a diagram for explaining the frame format ofdedicated traffic channel, and FIG. 1(b) is a diagram for explaining theframe format of common control channel.

In the GSM system, TACH (Traffic and Associated Channel) is defined asthe dedicated traffic channel, and FCCH (Frequency Correction Channel)and SCH (Synchronization Channel) are defined as the common controlchannel. In the dedicated traffic channel TACH, as shown in FIG. 1(a),the period of transmitting the transmission unit of frame from #1 to #26is designated as one GSM superframe. One frame has a duration of 8 BP(burst period). One BP is 0.577 ms. Therefore, one GSM superframe has atransmission period of 120 ms. In the common control channel FCCH/SCH,as shown in FIG. 1(b), the period of transmitting 8 BP frame from #1 to#51 is one FCCH/SCH superframe.

The observation method of different frequency components between GSM andGSM is described next. FIG. 2 is a diagram for explaining theobservation period of GSM superframe applied in the GSM system. FIG. 3shows an observation method of different frequency components betweenGSM and GSM. More specifically, FIG. 3(a) is a diagram for explainingthe frame format of common control channel. FIG. 3(b) is a diagram forexplaining the frame format of dedicated traffic channel in relation tothe common control channel. FIG. 3(c) is a diagram for explaining theobservation period inserted in every GSM superframe. FIG. 4 is a diagramfor explaining an observation example in the dedicated traffic channelof the GSM system. This FIG. 4 is disclosed in the publication “The GSMSystem for Mobile Communication” by Michel MOULY and Marie-BernadettePAUTET (international standard book number 2-9507190-0-7).

In the GSM system, the no-transmission period (idle period) assigned forone GSM superframe is 12 BP (=6.9 ms) as shown in FIG. 2. At the time ofhandover, different frequency component (control channel) of another GSMsystem is observed and detected by making use of this no-transmissionperiod. The FCCH/SCH superframe is composed of 51 frames (see FIG.3(a)). On the contrary, the GSM superframe (see FIG. 3(b)) has 52 framesin two periods. Comparing these two superframes, therefore, there is adifference of one frame. That is, the FCCH/SCH superframe is short ofone frame. Since the observation period is once in one GSM superframe,in two GSM superframes, the frequency is observed and detected two times(see FIG. 3(c)).

This observation and detection procedure is shown in FIG. 4. There is adifference of one frame between one FCCH/SCH superframe in commoncontrol channel and two GSM superframes in dedicated traffic. Theposition of the observation period assigned for one GSM superframe isfixed in the dedicated traffic channel TACH/F. Therefore, frequency isobserved in a specified frame of every GSM superframe. When the FCCH/SCHsuperframe is composed of the same number of frames as the two GSMsuperframes, the same frame number is observed between GSM and GSM allthe time. However, since there is a difference of one frame betweenFCCH/SCH superframe and two GSM superframes, observation is shifted byone frame each in every observation.

Incidentally, one FCCH/SCH superframe corresponds to two periods of GSMsuperframe so that the frequency is observed and detected twice in everyone FCCH/SCH superframe. That is, the time difference in this pair ofobservation periods is one GSM superframe, and the pair of observationsprogress in a form shifted by one period of one GSM superframe.Therefore, in a frequency handover between GSM and GSM, the frequency isobserved and detected in such a manner that the timing of theobservation and detection is shifted twice in every one period ofFCCH/SCH superframe and by one frame each in every one period.

The next-generation system, UMTS, is explained below. FIG. 5 shows aframe format applied in the UMTS. More specifically, FIG. 5(a) is adiagram for explaining the frame format of dedicated traffic channelapplied in the GSM system. FIG. 5(b) is a diagram for explaining theformat of superframe of UMTS.

In the GSM system, in the dedicated traffic channel TACH mentionedabove, as shown in FIG. 5(a), the period of transmitting the frames,which is the unit of transmission, from #1 to #26 is designated as oneGSM superframe. One frame has duration of 8 BP (burst period). In theUMTS, on the other hand, the UMTS superframe is composed of the sameperiod as in this GSM superframe. That is, in the UMTS, in all channels,as shown in FIG. 5(b), the period of transmitting frames from #1 to #12,each having duration of 10 ms, is one UMTS superframe.

The observation method of different frequency components between GSM andUMTS is described next. FIG. 6 shows the observation method of differentfrequency components between GSM and UMTS. More specifically, FIG. 6(a)is a diagram for explaining the frame format of common control channelapplied in the GSM system. FIG. 6(b) is a diagram for explaining therelation of superframe between the UMTS and GSM systems. FIG. 6(c) is adiagram for explaining the observation period inserted in everysuperframe in the UMTS.

As mentioned above, the FCCH/SCH superframe is composed of 51 frames(see FIG. 6(a)). On the contrary, the GSM superframe has 52 frames intwo periods (see FIG. 3(b)). The GSM superframe and UMTS superframe areequal in the duration of one period. Therefore, the relation between theFCCH/SCH superframe and the UMTS superframe coincides with the relationbetween the FCCH/SCH superframe and the GSM superframe explained above.That is, there is a difference of one frame in the FCCH/SCH superframeand two UMTS superframes (see FIG. 6(b)).

Herein, in frequency handover between UMTS and GSM, in order to obtainthe same function as in frequency handover between GSM and GSM mentionedabove, observation period of about 6.9 ms is required in one UMTSsuperframe. Accordingly, as shown in FIG. 6(c), observation anddetection is carried out twice in two UMTS superframes. Only when 12BP=6.9 ms, it is same as the handover between GSM and GSM.

In this handover between UMTS and GSM, however, due to restrictions oferror correction code and spreading factor, it is impossible to assignall necessary observation period for one frame in one superframe. Thatis, the operation for increasing the coding rate of the error correctioncode cannot be increased more than the number of information bits of thenon-coding case. Further, in the UMTS, the frame length is 10 ms, andsince the no-transmission period of about 6.9 ms for observation ofdifferent frequency components is more than half of the frame length,deterioration of interleaving performance is predicted. Further, inorder to prepare the no-transmission period of about 6.9 ms in oneframe, it is required to reduce the transmission period to about 3.1 ms.Therefore the transmission power in the compressed mode transmissionshould be increased. This results in a problem that the interferencepower on another channels is instantly increased.

It may be hence considered to observe and detect different frequencycomponents in one UMTS superframe by dividing in plural times. In thiscase, the time performance for compensating for control channel of GSMchannel is same as when preparing an observation period once in everyone UMTS superframe. Consequently, the number of idle slots forobtaining one observation period can be set smaller than in the casebetween GSM and GSM. The idle slots can be generated by using puncturedcode or higher coding rate of error correction coding.

In the first embodiment, the frequency is observed and detected twice inevery one UMTS superframe. Hence, in two UMTS superframes, the frequencyis observed and detected four times.

The observation and detection method is explained by referring to FIG.7. FIG. 7 is a diagram for explaining the frame transmission of downlinkin the first embodiment of the invention. In FIG. 7, the axis ofordinates denotes the transmission rate or transmission power, and theaxis of abscissas represents the time. There is a difference of oneframe between one FCCH/SCH superframe and two UMTS superframes in thecommon control channel. In the dedicated traffic channel TACH/F, theposition of observation period assigned in one GSM superframe is fixed.Similarly, in the UMTS also the positions of two observation periodsassigned in one UMTS superframe in the downlink traffic channel arefixed. Therefore, frequency is observed and detected in specified frames(two positions) of every UMTS superframe. Thus, since there is adifference of one frame between one FCCH/SCH superframe and two UMTSsuperframes, one frame is shifted each in each observation.

Since one FCCH/SCH superframe corresponds to two periods of UMTSsuperframe, the frequency is observed and detected four times in oneFCCH/SCH superframe. That is, the time difference in the pair ofobservation periods corresponds to one UMTS superframe in every UMTSsuperframe, and the pair of observations progress in a form shifted byone period of one FCCH/SCH superframe. Therefore, in frequency handoverbetween UMTS and GSM, the frequency is observed and detected four timesin every period of FCCH/SCH superframe, and while shifting by one frameeach in every period of observation.

The observation period, that is, the idle slot is set in the center of aspecified frame. Hence, interleaving effect is obtained in thecompressed mode frame transmission. Further, by increasing the codingrate in punctured coding or error correction coding, the redundancy isfurther decreased, and the idle period can be set longer proportionally.In this case, the quantity of information to be transmitted isdecreased, the spreading factor can be kept unchanged. That is, theinterference and noise resistant characteristic may be maintained.Incidentally, the characteristic deteriorates when transmittingcompressed frames so that the transmission power must be slightlyincreased as compared to the normal transmission.

A specific example of mobile communication system is discussed below.FIG. 8 is a block diagram showing a mobile radio communication systemaccording to the first embodiment of the invention. The mobile radiocommunication system consists of a transmitter 1 and a receiver 2. Sucha system is installed at both, a base station and a mobile station. Inthis mobile radio communication system, for example, W (wideband)-CDMA(code division multiple access) communication method is applied.

The transmitter 1 comprises, as shown in FIG. 8, a controller 11, anerror correction encoder 12, an interleaver 13, a framing/spreading unit14, a radio frequency transmitter 15, etc. The controller 11 controlsthe operation of the interleaver 13, framing/spreading unit 14, andradio frequency transmitter 15 mainly through negotiation with thereceiver 2. This controller 11 controls the operation suited to normalmode (non-compressed mode) and compressed mode by negotiation with thereceiver 2. More specifically, the controller 11 instructs thetransmission timing for transmitting the compressed mode frames, incompressed mode, to the framing/spreading unit 14. The controller 11also instructs increase of average transmission power when transmittingcompressed mode frames to the radio frequency transmitter 15.

The error correction encoder 12 obtains coded data by error correctioncoding of transmission data stream. The interleaver 13 permutes the timesequence of (interleaves) the coded data in bit units in order tominimize the effects of transmission error in the event of, for example,loss of continuous bits of transmission signal due to fading duringtransmission. The interleaver 13 has a memory for interleaving oneframe.

The framing/spreading unit 14 spreads wider by using a spreading code ofeach user, depending on normal mode or compressed mode, and forms aframe depending on each mode. When transmission timing depending on themode is instructed from the controller 11, this framing/spreading unit14 sends out the frame to the radio frequency transmitter 15 at thetransmission timing. The radio frequency transmitter 15 converts thetransmission signal obtained from the framing/spreading unit 14 intoradio frequency, and transmits. The radio frequency transmitter 15increases the average transmission power in the compressed mode ascompared with that of the normal mode according to the control of thecontroller 11, and outputs a transmission signal.

The receiver 2 comprises, as shown in FIG. 8, a controller 21, an errorcorrection decoder 22, a deinterleaver 23, a deframing/de-spreading unit24, a radio frequency receiver 25, etc. The controller 21 controls theoperation of the deinterleaver 23 and deframing/de-spreading unit 24mainly through negotiation with the transmitter 1. This controller 21controls the operation suited to the normal mode and compressed mode bynegotiation with the transmitter 1. More specifically, the controller 21instructs reception timing for receiving the compressed mode frames inthe compressed mode to the deframing/de-spreading unit 24.

The radio frequency receiver 25 demodulates the reception signal sentfrom an antenna not shown. The deframing/de-spreading unit 24 de-spreadsusing the spreading signal assigned to the user of the receiver 2depending on the normal mode or compressed mode, and forms a framesuited to each mode. When reception timing depending on each mode isinstructed from the controller 21, the deframing/de-spreading unit 24receives the reception signal from the radio frequency receiver 25 atthis reception timing.

The deinterleaver 23 permutes the time sequence (de-interleaves) of thecoded data in bit units in the reverse sequence of interleaving in thetransmitter 1. The deinterleaver 23, like the interleaver 13, has amemory for interleaving one frame. The error correction decoder 22decodes the de-interleaved signal, and obtains decoded data, that is,reception data stream.

Explained next is the frame transmission including compressed mode. Inthis mobile radio communication system, in compressed mode, a period oftransmitting intermittently by forming frames into slots is provided,and by making use of no-transmission period in this period, theintensity of different frequency carrier is measured. For this purpose,frames formed into slots must be compressed, but when interleaved sameas in ordinary transmission, sufficient interleaving time is notavailable, and enough interleaving effect cannot be obtained.

Accordingly, the transmission period of compressed frame in one frame isdivided. One portion is assigned at the beginning of a frame area, andthe other portion is set at the end of the same frame area, so that arequired interleaving time may be obtained. That is, the idle slotcorresponding to the observation period is placed in the center of aframe. In the receiver 2, this operation is reverse.

Herein, the relation between the number of idle slots and the number ofslots in the compressed mode frame is described. Supposing one frame tobe composed of 16 slots, the number of slots in the first half to be A,the number of idle slots to be B, and the number of slots in the secondhalf to be C, the following combinations can be considered. That is,(A, B, C)=(7, 1, 8)/(7, 2, 7)/(6, 3, 7)/(6, 4, 6)/(5, 5, 6)/(5, 6, 5)According to these combinations, for example, supposing the number ofslots in the first half and second half to be 7 slots and 8 slotsrespectively, one slot in the center of the frame is inserted as an idleslot.

When a short idle slot such as one or two slots is assigned per frame,only punctured coding may be used. The position of the idle slot inprinciple should be in the frame center, but it may be deviated forwardor backward.

In such short idle slot, by properly determining the compressed modeframe of first half and second half and position of the idle slot, thesame acquisition time as in the case of frequency handover between GSMand GSM may be obtained.

In the first embodiment, the compressed mode frame is divided into firstportion and second portion bounded by the idle slot within one frame.The following is to explain how to insert the observation period, thatis, the idle,slot in which frame in one UMTS superframe, and how todetermine the inserting position.

One UMTS superframe is composed of 12 frames. In the GSM, one GSMsuperframe is composed of 26 frames, and one frame is 8 BP long, andhence the total period is 208 BP. The idle slot equivalent to 8 BP isobserved in two compressed mode operation, and hence one observation in,compressed mode has an idle slot length equivalent to 4 BP. Thus, when afirst frame is specified arbitrarily in one UMTS superframe, theequation between the position of the second frame and the first frame isas shown in equation (1). In the case shown in equation (1), it isassumed that the frame number of the first portion is even, and theframe number in the second portion is odd. This equation (1) is4(2n+1)=K(208 BP)/122n+1=13K/3.   (1)In equation (1), the position that can be observed in the compressedmode of the first half is the same, but since the observation period is4 BP, half of 8 BP, and hence the equation shows the relation forobserving the portion of 4 BP that can be observed in the compressedmode in the second half, equivalently to 4 BP corresponding to thesecond half of 8 BP missing in the first half. That is, 4(2n+1) denotesan odd-number multiple of 4 BP (when the first half is even, the secondhalf is odd), and it suggests that the interval may be K times the UMTSframe length. When the UMTS frame length is expressed by BP, it is 208BP (number of BP of UMTS superframe)/12 (number of UMTS frames includedin UMTS superframe). Here, n is an arbitrary natural number.

When combinations of K and n that satisfy equation (1), two kinds ofcombination can be obtained as shown in equation (2). That is,(K, n)=(3, 6)/(9,19)   (2)According to equation (2), the frame three frames after the first framemay be defined as the second frame, or the frame nine frames after thefirst frame may be defined as the second frame. In FIG. 7, for example,supposing frame #2 to be the first frame, frame #5 is the second frame.

The compressed mode operation when observing and detecting from the UMTSto the GSM system is explained below. Herein, only the compressed modeis described. FIG. 9 is a flowchart for explaining the transmissionoperation in the compressed mode, and FIG. 10 is a flowchart forexplaining the reception operation in the compressed mode. In thecompressed mode of the transmitter 1 at the UMTS side (see FIG. 9),interleaving in one frame is instructed to the interleaver 13 (stepS101), and the interleaver 13 interleaves in one frame. When the timereaches the timing of either first half or second half of the firstframe timing or second frame timing to be observed (step S102), thetransmission timing is instructed to the framing/spreading unit 14 (stepS103).

Further, increase of average transmission power is instructed to theradio frequency transmitter 15 (step S103), and the frames aretransmitted at a higher power in the compressed mode than in the normalmode. Thus, the frequency is observed and detected twice in one UMTSsuperframe. In this compressed mode, the frames are transmittedintermittently (discontinuously).

On the other hand, in the compressed mode of the receiver 2 at the UMTSside (see FIG. 10), when the time reaches the timing of either firstportion or second portion of the first frame timing or second frametiming to be observed (step S111), the reception timing is instructed tothe deframing/de-spreading unit 24 (step S112). After receiving thesignal of the portion of one frame, deinterleaving by one frame isinstructed to the deinterleaver 23 (step S113), and the deinterleaver 23deinterleaves is one frame. Thus, in the compressed mode, the frames arereceived intermittently (discontinuously), and the signal of the GSMsystem is observed in an idle period.

As explained herein, according to the first embodiment, where the UMTSand another system coexist, an idle period for observing the frequencycomponent of the another system is inserted in the superframe of theUMTS. This idle period is at most half of one frame of the superframe ofUMTS and is inserted at an interval of certain frames. Hence it is notrequired to observe the frequency component by one observation in onesuperframe, and the restrictions, in frame transmission such as errorcorrection code and spreading factor can be satisfied. As a result, evenwhen the UMTS and an another system coexist, the frequency component ofthe another system can be securely observed from the UMTS, anddeterioration of interleaving performance of the compressed mode framecan be suppressed at this time.

Moreover, in one UMTS superframe, since the interval of the specifiednumber of frames is determined by the difference in the transmissionperiod between the UMTS and another system, different frequencycomponents can be observed completely depending on the difference in thetransmission period.

Since the idle slot time is placed in the center of the frame that isthe unit of superframe of UMTS, the interleaving effect can be obtainedsecurely.

In the superframe of UMTS, since plural idle periods are disposedseparately in each frame, a necessary idle duration can be held in onesuperframe.

The total of plural idle slot durations is set at about 6.9 ms equal tothe case of GSM, so that the equal idle duration for the observationperiod of different frequencies of other systems can be held in one UMTSsuperframe.

The frame in which the idle slot duration is inserted is compressed andtransmitted intermittently, and therefore even when idle period isinserted in the duration of one frame, frame transmission of highdecodability can be realized.

Since the compressed frame is generated by increasing the coding ratethe compression ratio is reduced, and the number of use of spreadingcodes of shorter code length can be suppressed.

In the compressed mode, moreover, frames compressed at the samespreading factor as in normal mode are generated, and therefore theinterference and noise resistant characteristic to the compressed framescan be assured.

Since the average transmission power is increased when transmittingcompressed mode frames, the characteristic deterioration can besuppressed to a minimum limit.

In the foregoing first embodiment, at the time of frequency handover,the observation period (about 6.9 ms) is divided into two portions inone UMTS superframe for observing and detecting frequency. However, theinvention is not limited to this embodiment alone. As a secondembodiment explained below, the observation period may be divided inmore than two portions. In the second embodiment, for example, theobservation period is divided into four portions. The entireconstitution in the second embodiment is same as in the firstembodiment, and only the difference in operation is described below.

The observation and detection method of the second embodiment isexplained below. FIG. 11 is a diagram for explaining the frametransmission of downlink according to the embodiment of the invention.In FIG. 11, the axis of ordinates denotes the transmission rate ortransmission power, and the axis of abscissas represents the time. Incomparison between one FCCH/SCH superframe and two UMTS superframes inthe common control channel, there is a difference of one frame. In thededicated traffic channel TACH/F, the position of observation periodassigned in one GSM superframe is fixed. Similarly in the UMTS, thepositions of four observation periods assigned in one UMTS superframe inthe downlink traffic channel are fixed. Therefore, the frequency isobserved and detected in specified frames (four positions) of every UMTSsuperframe. Thus, since there is a difference of one frame between oneFCCH/SCH superframe and two UMTS superframes, one frame is shifted eachin each observation.

Since one FCCH/SCH superframe corresponds to two periods of UMTSsuperframe, the frequency is observed and detected eight times in oneFCCH/SCH superframe. That is, in every UMTS superframe, the differencein the pair of observation periods corresponds to one UMTS superframe,and the pair of observations progress in a form shifted by one period ofone UMTS superframe. Therefore, in frequency handover between UMTS andGSM, the frequency is observed and detected eight times in everyFCCH/SCH superframe, and while shifting by one frame each in everyperiod of observation.

In the second embodiment, same as in embodiment 1, the compressed modeframe is divided into first portion and second portion bounded by theidle slot within one frame. The following is to explain how to insertthe observation period, that is, the idle slot in which frame of oneUMTS superframe, and how to determine the inserting position.

In the foregoing first embodiment, since one UMTS superframe is composedof 12 frames, the method of dividing the UMTS superframe by unit of aframe is employed. However, the UMTS superframe can be divided into ashorter time unit and a position for assigning the idle slot can be set.For example, since one frame in UMTS is composed of 16 slots, the UMTSsuperframe is divided by unit of a slot in the second embodiment.

The case of four divisions is shown in equation (3). It requires firstframe to fourth frame for assigning the each observation period in thiscase. Equation (3) shows a case in which the frame number of the firstframe is even. Equation (3) is an equation for determining the secondframe. In the same concept as in the first embodiment, this equation (3)is expressed as2(4n+1)=K1(208 BP)/12×164n+1=13K1/24.   (3)In equation (3), K1 shows the frame number of the second frame of UMTSsuperframe, and n is an arbitrary natural number. At the right side ofequation (3), since one frame is composed of 16 slots, it is multipliedby 12 frames in the denominator.

When combinations of K1 and n that satisfy equation (3) are calculated,two types of combination can be obtained as shown in equation (4). Thatis,(K1, n)=(24, 3)/(120, 16).   (4)In this case, since K1=24 indicates the number of slots, the secondframe can be determined by dividing K1 by 16. In the case of K1=24, thesolution is 1.5 frames, and when expressed by the frame number, theframe in which the second observation period is assigned is the frame1.5 frames after the first frame.

Equation (5) is for determining the third frame. This equation (5) is2(4n+2)=K2(208 BP)/12×162n+1=13K2/48.   (5)In equation (5), K2 denotes the frame number of the third frame of UMTSsuperframe, and n is an arbitrary natural number.

When combinations of K2 and n that satisfy equation (5) are calculated,two types of combination are obtained as shown in equation (6). That is,(K2, n)=(48, 6)/(144, 19).   (6)In this case, since K=48 indicates the number of slots, the third framecan be determined by dividing K by 16. In the case of K=48, the solutionis 3 frames, and when expressed by the frame number, the frame in whichthe third observation period is assigned is the frame 3 frames after thefirst frame.

Equation (7) is for determining the fourth frame. This equation (7) is2(4n+3)=K3(208 BP)/12×162n+1=13K3/48.   (7)In equation (7), K3 denotes the frame number of the fourth frame of UMTSsuperframe, and n is an arbitrary natural number.

When combinations of K3 and n that satisfy equation are calculated (7),two types of combination are obtained as shown in equation (8). That is,(K3, n)=(72, 9)/(168, 22).   (8)In this case, since K=72 indicates the number of slots, the fourth framecan be determined by dividing K by 16. In the case of K=72, the solutionis 4.5 frames, and when expressed by the frame number, the frame inwhich the fourth observation period is assigned is the frame 4.5 framesafter the first frame.

As explained herein, the number of divisions of observation period inone UMTS superframe can be four, and the same effects as in the firstembodiment are also obtained in this case. However, unlike the firstembodiment, the division interval is not the specified number of framesinterval, but is an interval of a specified number of slots.

In the foregoing second embodiment, at the time of frequency handover,the observation period (about 6.9 ms) is divided into four portions inone UMTS superframe for observing and detecting frequency in fourframes, but the invention is not limited to this embodiment alone.However, as a third embodiment explained below, the observation periodcan be divided in more than four portions. In the third embodiment, forexample, it is divided into eight portions. The entire constitution inthe third embodiment is same as in the first embodiment described above,and only the difference in operation is described below.

The observation and detection method of the third embodiment isexplained below. FIG. 12 is a diagram for explaining the frametransmission of downlink in the third embodiment of the invention. InFIG. 12, the axis of ordinates denotes the transmission rate ortransmission power, and the axis of abscissas represents the time. Asmentioned above, in comparison between one FCCH/SCH superframe and twoUMTS superframes in the common control channel, there is a difference ofone frame. In the dedicated traffic channel TACH/F the position ofobservation period assigned in one GSM superframe is fixed. Similarly,in the UMTS, the positions of eight observation periods assigned in oneUMTS superframe in the downlink traffic channel are fixed. Therefore,the frequency is observed and detected in specified frames (fourpositions) of every UMTS superframe. Thus, since there is a differenceof one frame between one FCCH/SCH superframe and two UMTS superframes,one frame is shifted each in each observation.

Since one FCCH/SCH superframe corresponds to two periods of UMTSsuperframe, the frequency is observed and detected 16 times in oneFCCH/SCH superframe. That is, in every UMTS superframe, the differencein the set of observation periods corresponds to one UMTS superframe,and the set of observations progress in a form shifted by one period ofone UMTS superframe. Therefore, in frequency handover between UMTS andGSM, the frequency is observed and detected 16 times in every period ofFCCH/SCH superframe, while shifting by one frame each in every period ofobservation.

In the third embodiment, too, same as in the foregoing first and secondembodiments, the compressed mode frame is divided into first portion andsecond portion bounded by the idle slot within one frame. The followingis to explain how to insert the observation period, that is, the idleslot in which frame in one UMTS superframe, and how to determine theinserting position.

In the third embodiment, same as in the foregoing second embodiment, theUMTS superframe is divided by the shorter time unit, and the positionfor placing the idle slot is set.

Thus, in the third embodiment, the number of divisions of observationperiod in one UMTS superframe can be eight, and the same effects as inthe first embodiment are also obtained in this case. However, unlike thefirst embodiment, the division interval is not the specified number offrames interval, but is an interval of a specified number of slots.

In the foregoing first to third embodiments, the observation period isdivided up to eight divisions, but the invention is not limited to theseexamples only. The number of divisions may be further increased asrequired on the basis of the smaller unit than the slot.

The invention is thus described while referring to preferredembodiments, but the invention may be modified in various forms withinthe claimed scope, and such changes shall not be excluded from the scopeof the invention.

As described herein, according to the mobile radio communication systemin one aspect of the invention, in the case where the firstcommunication system and second communication system coexist, since theidle period for observing the frequency component of the secondcommunication system is inserted at most in ½ time of one frame durationfor composing one superframe of first communication system, at intervalsof a specified number of frames, it is not required to observe thefrequency component by one observation in one superframe, and therestrictions in frame transmission such as error correction code andspreading factor can be satisfied. Therefore, even when the firstcommunication system and second communication system coexist, thefrequency component of the second communication system can be securelyobserved from the first communication system. Further, deterioration ofinterleaving performance of the compressed mode frame during suchobservation can be suppressed.

According to the mobile radio communication in another aspect of theinvention, in the case where the UMTS and another system coexist, sincethe idle period for observing the frequency component of the anothersystem is inserted at most in ½ time of one frame duration for composingone superframe of UMTS, at intervals of a specified number of frames, itis not required to observe the frequency component by one observation inone superframe, and the restrictions in frame transmission such as errorcorrection code and spreading factor can be satisfied, and thereforeeven when the UMTS and another system coexist, the frequency componentof the another system can be securely observed from the UMTS, anddeterioration of interleaving performance of the compressed mode framecan be suppressed at this time.

According to the mobile radio communication apparatus in another aspectof the invention, since the interval of a specified number of frames isdetermined by the difference in the transmission period between the UMTSand another system, the different frequency components can be observedcompletely depending on the difference in the transmission period.

According to the mobile radio communication apparatus in another aspectof the invention, since the idle period is placed in the center of theframe that is the unit of superframe of the UMTS, the interleavingeffect is obtained securely.

According to the mobile radio communication apparatus in a differentaspect of the invention, in the case where the first communicationsystem and second communication system coexist, since the idle periodfor observing the frequency component of the second communication systemis inserted at most in ½ time of one frame duration for composing onesuperframe of first communication system, at intervals of a specifiednumber of slots, it is not required to observe the frequency componentby one observation in one superframe, and the restrictions in frametransmission such as error correction code and spreading factor can besatisfied. Therefore even when the first communication system and secondcommunication system coexist, the frequency component of the secondcommunication system can be securely observed from the firstcommunication system. Further, deterioration of interleaving performanceof the compressed mode frame during such observation can be suppressed.

According to mobile radio communication apparatus in another aspect ofthe invention, in the case where the UMTS and another system coexist,since the idle period for observing the frequency component of theanother system is inserted at most in ½ time of one frame duration forcomposing one superframe of UMTS, at intervals of a specified number ofslots, it is not required to observe the frequency component by oneobservation in one superframe, and the restrictions in frametransmission such as error correction code and spreading factor can besatisfied, and therefore even when the UMTS and another system coexist,the frequency component of the another system can be securely observedfrom the UMTS, and deterioration of interleaving performance of thecompressed mode frame can be suppressed at this time.

According to the mobile radio communication system in another aspect ofthe invention, since the interval of a specified number of slots isdetermined by the difference in the transmission period between the UMTSand another system, the different frequency components can be observedcompletely depending on the difference in the transmission period.

According to the mobile radio communication system in another aspect ofthe invention, since the plural idle periods in the superframe of theUMTS are placed separately in each frame, the necessary idle duration isheld in one superframe.

According to the mobile radio communication system in another aspect ofthe invention, since the total of the plural idle periods is equal tothe specified idle duration provided for observing the frequencycomponent between the other systems, an idle period equal to theobservation of different frequencies of other systems can be held in onesuperframe.

According to the mobile radio communication system in another aspect ofthe invention, since the frame in which the specified time is insertedis compressed and transmitted intermittently, a frame transmission of ahigh decodability is realized even when an idle period is inserted inone frame period.

According to the mobile radio communication system in another aspect ofthe invention, since the compressed frame is generated by increasing thecoding rate, the compression rate is lowered, and the number ofspreading codes of a shorter code length can be suppressed.

According to the mobile radio communication system in another aspect ofthe invention, since the compressed frame is generated at a samespreading factor as another frame in which the specified idle durationis not inserted, the interference and noise resistant characteristic tothe compressed frame is assured.

According to the communication apparatus applied in a mobile radiocommunication system according to another aspect of the invention, inthe case where the first communication system and second communicationsystem coexist, since it is controlled so that the idle period forobserving the frequency component of the second communication system isinserted at most in ½ time of one frame duration for composingsuperframe in the superframe of the first communication system, it isnot required to observe the frequency component by one observation inone superframe, and the restrictions in frame transmission such as errorcorrection code and spreading factor can be satisfied. Therefore, evenwhen the first communication system and second communication systemcoexist, the frequency component of the second communication system canbe securely observed from the first communication system. Further,deterioration of interleaving performance of the compressed mode frameduring such observation can be suppressed.

According to the communication apparatus applied in a mobile radiocommunication system according to another aspect of the invention, inthe case where the UMTS and another system coexist, since the idleperiod for observing the frequency component of the another system isinserted at most in ½ time of one frame duration for composing onesuperframe of UMTS, at intervals of a specified number of frames, it isnot required to observe the frequency component by one observation inone superframe, and the restrictions in frame transmission such as errorcorrection code and spreading factor can be satisfied. Therefore, evenwhen the UMTS and another system coexist, the frequency component of theanother system can be securely observed from the UMTS. Further,deterioration of interleaving performance of the compressed mode frameduring such observation can be suppressed.

According to the communication apparatus applied in a mobile radiocommunication system according to another aspect of the invention, sincethe interval of a specified number of frames is determined by thedifference in the transmission period between the UMTS and anothersystem at the time of controlling, the different frequency componentscan be observed completely depending on the difference in thetransmission period.

According to the communication apparatus applied in a mobile radiocommunication system according to another aspect of the invention, sincethe specified idle period is placed in the center of the frame which isthe unit of superframe of the UMTS at the time of controlling, theinterleaving effect may be obtained securely.

According to the communication apparatus applied in a mobile radiocommunication system according to another aspect of the invention, inthe case where the first communication system and second communicationsystem coexist, since it is controlled so that the idle period forobserving the frequency component of the second communication system isinserted at most in ½ time of one frame duration for composingsuperframe in the superframe of the first communication system and at aninterval of a specified number of slots, it is not required to observethe frequency component by one observation in one superframe, and therestrictions in frame transmission such as error correction code andspreading factor can be satisfied. Therefore even when the firstcommunication system and second communication system coexist, thefrequency component of the second communication system can be securelyobserved from the first communication system. Further, deterioration ofinterleaving performance of the compressed mode frame during suchobservation can be suppressed.

According to the communication apparatus applied in a mobile radiocommunication system according to another aspect of the invention, inthe case where the UMTS and another system coexist, since the idleperiod for observing the frequency component of the another system isinserted at most in ½ time of one frame duration for composing onesuperframe of first communication system, at intervals of a specifiednumber of frames of UMTS, at intervals of a specified number of slots,it is not required to observe the frequency component by one observationin one superframe, and the restrictions in frame transmission such aserror correction code and spreading factor can be satisfied. Therefore,even when the UMTS and another system coexist, the frequency componentof the another system can be securely observed from the UMTS. Further,deterioration of interleaving performance of the compressed mode frameduring such observation can be suppressed.

According to the communication apparatus applied in a mobile radiocommunication system according to another aspect of the invention, sincethe interval of a specified number of slots is determined by thedifference in the transmission period between the UMTS and anothersystem at the time of controlling, different frequency components can beobserved completely depending on the difference in the transmissionperiod.

According to the communication apparatus applied in a mobile radiocommunication system according to another aspect of the invention, sinceplural idle periods are disposed in separate frames in the superframe ofthe UMTS at the time of controlling, a necessary idle duration can beheld in one superframe.

According to the communication apparatus applied in a mobile radiocommunication system according to another aspect of the invention, sincethe total of the plural idle periods is set equal to the specified idleduration provided for observing the frequency component between theother systems at the time of controlling, an idle duration equal toobservation of different frequencies between other systems can be heldin one superframe.

According to the communication apparatus applied in a mobile radiocommunication system according to another aspect of the invention, sincethe compressed frame is generated by increasing the coding rate at thetime of controlling, the compression rate is lowered, and the number ofspreading codes of a shorter code length can be suppressed.

According to the communication apparatus applied in a mobile radiocommunication system according to another aspect of the invention, sincethe compressed frame is generated at a same spreading factor as anotherframe in which the specified idle duration is not inserted at the timeof controlling, the interference and noise resistant characteristic tothe compressed frame is assured.

According to the communication apparatus applied in a mobile radiocommunication system according to another aspect of the invention, sincethe average transmission power is increased in the compressed mode atthe time of controlling, the characteristic deterioration may besuppressed to a minimum limit.

According to the mobile radio communication method according to aspectof the invention, by compressing the frames to be transmittedintermittently at the time of compressed mode, and inserting an idleperiod for observing the frequency component of the second communicationsystem at most in ½ time of one frame duration for composing thesuperframe of the first communication system in the superframe of thefirst communication system and at an interval of a specified number offrames determined by the relation of the frame structure between thefirst communication system and second communication system, since thestep for transmitting intermittently the compressed frames is set up, itis not required to observe the frequency component by one observation inone superframe, and the restrictions in frame transmission such as errorcorrection code and spreading factor can be satisfied. Therefore, evenwhen the first communication system and second communication systemcoexist, the frequency component of the second communication system canbe securely observed from the first communication system. Further,deterioration of interleaving performance of the compressed mode frameduring such observation can be suppressed.

According to the mobile radio communication method according to anotheraspect of the invention, by compressing the frames to be transmittedintermittently at the time of compressed mode, and inserting an idleperiod for observing the frequency component of the second communicationsystem at most in ½ time of one frame duration for composing thesuperframe of the first communication system in the superframe of thefirst communication system and at an interval of a specified number ofslots determined by the relation of the frame structure between thefirst communication system and second communication system, since thestep for transmitting intermittently the compressed frames is set up, itis not required to observe the frequency component by one observation inone superframe, and the restrictions in frame transmission such as errorcorrection code and spreading factor can be satisfied. Therefore, evenwhen the first communication system and second communication systemcoexist, the frequency component of the second communication system canbe securely observed from the first communication system. Further,deterioration of interleaving performance of the compressed mode frameduring such observation can be suppressed.

According to the mobile radio communication method according to anotheraspect of the invention, in particular, in the case where the UMTS andanother system coexist, since the idle period for observing thefrequency component of the another system is inserted at most in ½ timeof one frame duration for composing one superframe of UMTS, at intervalsof a specified number of frames or at an interval of a specified numberof slots, it is not required to observe the frequency component by oneobservation in one superframe, and the restrictions in frametransmission such as error correction code and spreading factor can besatisfied. Therefore, even when the UMTS and another system coexist, thefrequency component of the another system can be securely observed fromthe UMTS. Further, deterioration of interleaving performance of thecompressed mode frame during such observation can be suppressed.

According to the mobile radio communication method according to anotheraspect of the invention, since the compressed frame is generated byincreasing the coding rate at this step, the compression ratio islowered, and the number of spreading codes of a shorter code length canbe suppressed.

According to the mobile radio communication method according to anotheraspect of the invention, since the compressed frame is generated at asame spreading factor as another frame in which the specified idleperiod is not inserted at this step, the interference and noiseresistant characteristic to the compressed frame is assured.

According to the mobile radio communication method according to anotheraspect of the invention, since the average transmission power isincreased in the compressed mode at this step, the characteristicdeterioration may be suppressed to a minimum limit.

INDUSTRIAL APPLICABILITY

As described herein, the mobile radio communication system, thecommunication apparatus applied in the mobile radio communicationsystem, and the mobile radio communication method of the invention areuseful for observing the control channel of another system by making useof idle period in the mobile radio communication system. In particularthis invention can suitably used in the mobile radio communicationsystem in which the UMTS (Universal Mobile Terrestrial communicationSystem) and GSM (Group Specific Mobile) system coexist.

1. A mobile radio communication system employing a CDMA method,comprising a transmitter (1) transmitting a plurality of frames in anormal mode and a plurality of compressed frames in a compressed modewithin a first frame transmission period, which is formed of pluralframes and required to transmit a predetermined number of frames, and areceiver (2) receiving said frames and said compressed framestransmitted by said transmitter (1), said transmitter (1) comprises aninterleaver (13) which performs interleaving of data in a frame in bitunits; a spreading unit (14), in which a plurality of frames processedby said interleaver (13) are inputted, wherein said spreading unit (14)compresses frames within said first frame transmission period to producecompressed frames, and divides each of said compressed frames into twodivided parts, and allocates one of said divided parts at the beginningof a frame period and the other one of said divided parts at the end ofsaid frame period, and creates, into each of said compressed frames, anidle period whose length is half as much as that of each frame or less,in a compressed mode; and a radio frequency transmitter (15) whichtransmits said compressed frames processed by said spreading unit (14)in said compressed mode; and said receiver (2) comprises a radiofrequency receiver which monitors, within said idle period in each ofsaid compressed frames, a frequency component in a control channel, saidcontrol channel having a second frame transmission period and beingemployed in a different mobile radio communication system.
 2. The mobileradio communication system according to claim 1, wherein said differentmobile radio communication system is GSM system.
 3. A receiver used in amobile radio communication system employing a CDMA method, wherein atransmitter (1) of said mobile radio communication system transmits aplurality of frames in a normal mode and a plurality of compressedframes in a compressed mode during a first frame transmission period,which is formed of plural frames, performs interleaving of data to betransmitted in bit units, and said first frame transmission period isdefined as a period required to transmit a predetermined number offrames, said receiver comprises: a radio frequency receiver (25), towhich said compressed frames received by an antenna are inputted, formonitoring a frequency component in a control channel within an idleperiod in each of said compressed frames within said first frametransmission period, wherein said control channel has a secondtransmission period which is employed in a different mobile radiocommunication system, and each of said compressed frames has an idleperiod whose length is half as much as that of each frame or less, andeach of said compressed frames is divided into two divided parts suchthat one of the divided parts is allocated at the beginning of a frameperiod and the other one of said divided parts is allocated at the endof said frame period.
 4. A transmitter used in a mobile radiocommunication system employing a CDMA method, wherein said transmitter(1) transmits a plurality of frames in a normal mode and a plurality ofcompressed frames in a compressed mode within a first frame transmissionperiod, which is formed of plural frames, and said first transmissionperiod is defined as a period required to transmit a predeterminednumber of frames, said transmitter (1) comprises: an interleaver (13)which performs interleaving of data in a frame in bit units; and aspreading unit (14), in which a plurality of frames processed by saidinterleaver (13) are inputted, wherein said spreading unit (14)compresses frames within said first frame transmission period to producecompressed frames, divides each of said compressed frames into twodivided parts, allocates one of said divided parts at the beginning of aframe period and the other one of said divided parts at the end of saidframe period, and creates, into each of said compressed frames, an idleperiod whose length is half as much as that of each frame or less, in acompressed mode; and a radio frequency transmitter (15) which transmitssaid compressed frames processed in said spreading unit (14) in saidcompressed mode.
 5. A mobile radio communication method used in a CDMAsystem, wherein said system includes a transmitter (1) which performsinterleaving of data to be transmitted in bit units, and transmits aplurality of frames in a normal mode and a plurality of compressedframes in a compressed mode within a first frame transmission period,which is formed of plural frames, and a receiver (2) that receives saidframes and said compressed frames transmitted by said transmitter (1),said first frame transmission period is defined as a period required totransmit a predetermined number of frames, said mobile radiocommunication method comprises: steps, executed by said transmitter (1),for compressing frames within said first frame transmission period;dividing each of said compressed frames into two divided parts forallocating one of said divided parts at the beginning of a frame periodand the other one of said divided parts at the end of said frame period;allocating in each of said frames an idle period whose length is half asmuch as that of each frame or less; transmitting said frames with saididle period to said receiver (2); and a step, executed by said receiver(2) for monitoring frequency components in a control channel having asecond frame transmission period within said idle period allocated ineach of said compressed frames, wherein said second frame transmissionperiod is employed in a different mobile radio communication system. 6.A mobile radio communication method used in a receiver (2) for a CDMAsystem, wherein a transmitter (1) of said mobile radio communicationsystem transmits a plurality of frames in a normal mode and a pluralityof compressed frames in a compressed mode during a first frametransmission period, which is formed of plural frames, and said firstframe transmission period is defined as a period required to transmit apredetermined number of frames, performs interleaving of data to betransmitted in bit units, said mobile radio communication methodcomprises: receiving said compressed frames within said first frametransmission period, each of said compressed frames having an idleperiod whose length is half as much as that of each frame or less andbeing divided into at least two parts such that one of said dividedframes is allocated at the beginning of a frame period and the other oneof said divided parts is allocated at the end of said frame period; andmonitoring a frequency component in a control channel within said idleperiod in each of said compressed frames, wherein said control channelhas a second frame transmission period which is employed in a differentmobile radio communication system.
 7. A mobile radio communicationmethod used in a transmitter (1) for a CDMA system, wherein saidtransmitter (1) transmits a plurality of frames in a normal mode and aplurality of compressed frames in a compressed mode within a first frametransmission period, which is formed of plural frames, and said firstframe transmission period is defined as a period required to transmit apredetermined number of frames, said mobile radio communication methodcomprises: generating said compressed frames through processes ofcompressing a plurality of frames within said first transmission period,dividing each of said compressed frames into at least two parts forallocating one of said divided parts at the beginning of a frame periodand the other one of said divided parts at the end of said frame period,and creating in each of said compressed frames an idle period whoselength is half as much as that of each frame or less, and; transmittingsaid compressed frames generated by said generating step.